The long-term objectives of this program are to identify and characterize the behavioral, pharmacological, and environmental factors that affect drug-taking behavior. The more immediate goals are: 1) to characterize the pharmacological and behavioral factors acting on narcotic tolerance as it influences various forms of operant behavior with special emphasis upon narcotic self-injection in the rhesus monkey; 2) to determine the effects of narcotic withdrawal induced by narcotic deprivation or by narcotic antagonists upon operant responding controlled by narcotic injections or by other consequences; and 3) to study various forms of aversive control of responding by narcotic antagonists in the presence of various degrees of narcotic dependence.